SHM and Waves: Quick Revision of Formulae for IIT JEE, UPSEE & WBJEE

Dec 21, 2016 18:20 IST

Hariom Singh

Find unitwise concepts and formulae from the chapter Simple Harmonic Motion and Waves. These concepts and formulae are very important in quick revision of complete unit. Once you have gone through chapters thoroughly and understood it well there is no need to study it again and again. You can only revise important formulas and terms which will save your precious time.

These formulae will be helpful in various engineering entrance examinations. In UPSEE and WBJEE where most of questions are asked directly on formulae, this quick revision note is very important.

SHM and Waves

Simple harmonic motion is a special type of periodic motion, in which a particle moves to and fro repeatedly about a mean position under a restoring force

Restoring force is directly proportional to displacement of the particle from mean position

Mathematically, F = – kx

Velocity in simple harmonic motion is defined as the time rate of change of its displacement at that instant. Mathematically,

Acceleration insimple harmonic motion is defined as the rate of change of its velocity at that instant. Mathematically,

Potential energy in simple harmonic motion is due to the displacement of the particle from its mean position. Mathematically,

Kinetic energy in simple harmonic motion is due to the velocity of the particle. Mathematically,

Work Function: A certain minimum amount of energy is required to be given to an electron to pull it out from the surface of the metal. This minimum energy required by an electron to escape from the metal surface is called the work function of the metal.

There are three types of electronic emissions:

(a) Thermionic emission

(b) Field emission

(c) Photo-electric emission

Photoelectric Effect

All the photosensitive substances such as lithium, sodium, potassium, caesium and rubidium emit electrons when they are illuminated by light. After the discovery of electrons, these electrons were termed as photoelectrons. The phenomenon is called photoelectric effect.

The number of photoelectrons emitted per second is directly proportional to the intensity of incident radiation.

Einstein’s Photoelectric Equation: Energy Quantum of Radiation

According to Einstien: Radiation energy is built up of discrete units – the so called quanta of energy of radiation. Each quantum of radiant energy has energy hν, where h is Planck’s constant and ν the frequency of light.